Study On The Deformation Detection Method Of Multi-Baseline Radar

The pace of economic growth has accelerated in China,and rail transit is one of the most important means of transportation,which is of great value to China's national economy.If the high-speed railway is deformed,it will lead to catastrophic consequences such as line deformation,which will affect the normal running of the train and cause a accident.Traditional leveling requires a lot of manpower,material resources and resources,and is susceptible to weather and other factors.Among the modern terrain deformation detection methods,microwave remote sensing technology is one of the important measurement methods.Synthetic Aperture Radar(SAR)are all-weather and full-time.The interferometric SAR measurement technology can be used to obtain small deformations on the ground.However,this technology requires spaceborne or airborne platforms,and the data processing is complex and computationally intensive.Aiming at the above problems,this thesis studies a new method of railway deformation measurement based on phase analysis.This method directly extracts the echo delay and phase information by using the radar arranged on the train,obtains the three-dimensional of the radar by solving the calibration point distance equation and calculates the deformation.The measurement accuracy of this method is similar to or higher than the interference technique.In this regard,the core work and innovation of this thesis are as follows:1.The pulse compression technique commonly used in synthetic aperture radar imaging is introduced.The factors affecting the range resolution and azimuth resolution of SAR imaging are analyzed.Three common SAR imaging algorithms are described: distance Doppler algorithm,Chirp Scaling algorithm and the backward projection algorithm.And the advantages of the backward projection algorithm are given.2.Analysis of deformation detection based on interferometric SAR.The basic principles of interferometric SAR imaging,as well as common operating modes,are described.The basic concept of coherence of interferometric SAR measurement system is introduced.Several basic methods for deformation measurement using SAR are briefly introduced.Finally,the experimental results of the interferometric SAR deformation measurement are verified by experimental simulation.3.The multi-baseline radar deformation detection method is discussed.Firstly,the system structure and model are introduced in detail,and the deformation of four antennas is researched.Then we discuss the selection of antenna transmit signals.In order to meet the high-precision ranging and solve the distance blur problem,this thesis will combine pulse compression and frequency sweep technology to extract more accurate distance information.Then the deformation are calculated according to the system model,and the algorithm flow based on the multi-baseline radar deformation detection method is clarified.Finally,the simulation of the ranging and deformation measurement method is carried out,and the factors affecting the performance of ranging and deformation measurement are given.The deformation measurement accuracy is affected by the ground distance error and the radar baseline length,and the ranging accuracy is affected by the transmitted signal bandwidth.4.The experimental results of deformation measurement show that the relative error of deformation increases with the increase of absolute distance error.The deformation relative error increases with increasing distance error and its three components are 2.04%,0.82% and 2.36% when the absolute distance error is 0.02 meters(1 meter baseline).The deformation relative error decreases with increasing length of baseline.The variations of deformation relative error tend to be flat when the length of baseline is above 1 meter and therefore the increasing length of baseline has little influence on deformation relative error.